JP3096062B2 - Deflection system with controlled beam spot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens action on an electron beam for controlling the shape and size of a spot formed by, for example, an electron beam incident (landing) on a display screen of a cathode ray tube (CRT). Electron beam lensing) due to magnetic field inhomogeneities.

The enlargement and distortion of the spot are caused, for example, by the screen being inclined or by repulsion due to space charge. Reducing spot enlargement and distortion when the electron beam is deflected by the deflection yoke is required, for example, in high definition television (HDTV).

In deflection systems using self-converging yokes, dynamic focusing and stigmators have been developed to prevent over-focusing and "flare" that degrade high resolution images. However, such systems distort the spots at both edges of the horizontal axis of the screen. For example, at the 3 o'clock point at the end of the horizontal axis of the display screen, the spot becomes horizontally elongated and elongated, having a width about twice the spot width at the center of the screen. Such distortion is unacceptable in high resolution displays.

In a deflection yoke that is anastigmatic (ie, various astigmatisms, image distortions have been corrected to a spot close to a circle), each of the horizontal and vertical deflection coils has a corresponding so-called , Uniform magnetic field,
That is, a magnetic field having no very large magnetic flux density gradient is generated. The deflecting magnetic field which is close to the uniform magnetic field has a winding distribution, that is, the angular density of the winding conductor is determined by the Fourier series (Fourier series).
According to es expansion, a deflection coil is created which contains only the fundamental or first harmonic component.

In the Fourier series, the n-th harmonic may be related to the winding distribution or the n-th order Fourier component of the winding-current product distribution. Such winding distribution or winding-
The ampoule distribution is periodic, for example, as a function of angle measured from the horizontal axis of the yoke. The term winding-current product, typically represented by the notation NI, refers to the value obtained by multiplying the current in a given winding turn by the number of turns. It is measured in ampere turns. The term winding-current product or winding-current product distribution is used to refer to the winding of such a winding, for example, with respect to a current component flowing at a horizontal or vertical frequency.

A change in the beam landing position caused only by a change in the basic Fourier component of the winding-current product distribution tends to elongate the beam spot. For example, in some prior art deflection systems that use only a uniform deflection magnetic field in the main deflection area, for example, the length of the long axis of the spot formed at the 3 o'clock point, as shown in FIG. It tends to stretch horizontally by about 1.5 times the long axis of the spot. In this case, the spots are stretched in the direction of deflection at various locations on the display screen such that the major axis of the elliptical spot coincides with the direction of deflection. The direction of deflection for a given spot is the direction formed between the spot and the center of the display screen. As shown in FIG. 1, the ratio of the major axis length of the spot to the minor axis length of the spot tends to increase as the beam spot is deflected away from the center of the screen and toward the side edges. For example, the ratio at the center of the screen is equal to 1 because the spot is round, while 3
In terms of time, it is 1.48 / 0.86, or about 1.7. This ratio defines the ellipticity of the spot. As the value of this ratio increases, the ellipticity of the spot increases. This difference in the ratio indicates the degree of distortion of the spot shape described above.

As described above, when only a uniform deflection magnetic field is used as the horizontal and vertical main deflection magnetic fields, the beam spot at the peripheral portion of the screen has an elliptical shape instead of a circular shape as shown in FIG. Using a barrel-shaped horizontal or vertical deflection magnetic field instead of a uniform horizontal or vertical deflection magnetic field reduces the degree of extension of the beam spot on the horizontal axis and the vertical axis, and reduces the beam spot closer to a circle. The use of a pincushion-type horizontal deflection magnetic field and a vertical deflection magnetic field reduces the degree of extension of the beam spot at a position along the diagonal line of the screen, thereby reducing a beam spot that is also nearly circular. It is known that it can be formed.

The present invention uses a pincushion-type horizontal deflection magnetic field and a vertical deflection magnetic field to reduce the degree of extension of a beam spot at a position along a diagonal line of a screen, and further uses a quadrupole configuration 28 described later for a deflection yoke. By changing the shape of each deflection magnetic field when the beam spot is on the horizontal axis and the vertical axis into a barrel shape, the degree of extension of the beam spot on the horizontal axis and the vertical axis is reduced, and To form a beam spot close to.

Using the quadrupole configuration, the beam spot at each end on the horizontal and vertical axes (at 3 o'clock, 9 o'clock, and 12 o'clock, 6 o'clock in FIG. 1) is deflected by deflection astigmatism. Flares may occur. The flare of such a beam spot, due to the quadrupole configuration, each deflection magnetic field is excessively barreled at the ends on the horizontal axis and the vertical axis,
It has been found that the extension of the beam spot at the ends on the horizontal and vertical axes is due to excessive reduction.

In view of this, the present invention particularly provides an astigmatism referred to as a stigmator which generates a quadrupole magnetic field for correcting deflection astigmatism at the front of the deflection yoke in order to prevent the occurrence of the beam spot flare. The correction device 24 is disposed to effectively reduce excessive barreling of each deflection magnetic field at the end of each axis, thereby reducing the flare of the beam spot at the end of each axis, and further shaping the shape of the beam spot. It will improve.

According to one aspect of the present invention, the first path of the electron beam path
A first non-uniform magnetic field is generated in the region. This first non-uniform magnetic field provides an electron beam lensing effect on the display screen that tends to converge the beam spot in the direction of the spot extension. A second non-uniform magnetic field is formed in a second region of the electron beam path that is further from the display screen than the first region. This second non-uniform magnetic field provides an electron beam lensing effect that tends to diverge the beam spot in the direction of the spot extension. The inhomogeneity of each of these fields is such that a given cross section of the electron beam, i.e., the profile in the profile, is reduced so that the major axis of the spot is less likely to be elongated and the ellipticity is increased. The parts are deflected by somewhat different amounts from each other. Therefore, the spot shape distortion is reduced.

In an implementation of another aspect of the invention, a first non-uniform deflection field non-uniformity is generated in a first quadrupole configuration and a second non-uniform magnetic field is generated in a second quadrupole configuration. Thus, the two configurations behave similarly to a quadrupole doublet.

In embodying features of the present invention, a first non-uniform magnetic field is formed between the exit and entrance regions of the deflection yoke so that a useful electron beam lens action to reduce spot ellipticity is obtained. I do. For example, the non-uniformity of the deflection magnetic field required for converging the beam spot, that is, the magnetic flux density gradient, can be varied depending on the position of the spot on the screen. For example, at the corners of a display screen having an aspect ratio of 4: 3, the type of non-uniform deflection field required in the yoke can be formed by a combination of pincushion horizontal and vertical deflection fields. On the other hand, when the spot is on each of the vertical and horizontal axes of the screen, a barrel-shaped horizontal and vertical deflection field will be required. Here, the terms barrel and pincushion mainly indicate the type or orientation of the deflection magnetic field gradient. For example, the barrel-type horizontal deflection magnetic field is
A horizontal deflection field formed in and around the beam at a given location of the yoke and decreasing along the horizontal axis of the yoke as a function of distance from the center of the yoke.

FIG. 1 shows the shape of a beam spot at a corresponding beam landing position obtained with a prior art deflection device using a uniform main deflection magnetic field.

FIG. 2 is a block diagram of a deflection device embodying aspects of the present invention and including a quadrupole coil configuration.

FIG. 3 is a diagram showing a quadrupole magnetic field generated by the configuration of FIG. 2 and its influence on the cross section of the electron beam.

FIG. 4 is a diagram showing a winding-current product distribution in one quadrant of the quadrupole coil of FIG.

5a to 5d show useful waveforms for explaining the operation of the configuration of FIG.

6a and 6b show a double quadrupole configuration having eight magnetic poles included in the configuration of FIG.

7a to 7e show other waveforms useful for explaining the operation of the arrangement of FIG.

FIG. 8 shows the shape of the beam spot at the corresponding beam landing position when the main deflection magnetic field is of the type generated in the configuration of FIG.

FIG. 9 is a block diagram of a deflection system embodying another aspect of the present invention.

FIG. 10 shows the shape of the beam spot at the corresponding beam landing position in the main deflection magnetic field generated in the configuration of FIG.

FIG. 11 shows the deflection yoke having the configuration shown in FIG.
2 shows the deflection magnetic field function as a function of the position at.

12a to 12d show a winding-current product distribution which gives the corresponding harmonic ratio necessary to reduce the beam spot elongation in a given quadrant of the corresponding deflection winding of the configuration of FIG. Is shown.

FIG. 13 is a block diagram of a deflection system embodying another embodiment of the present invention.

FIG. 14 is a diagram useful for explaining the operation of each double quadrupole configuration of the configuration of FIG.

FIG. 15 is a view showing the operation of a quadrupole doublet formed by a pair of double quadrupoles having the configuration shown in FIG.

FIG. 16 shows the shape of a beam spot at a corresponding beam landing position in a main deflection magnetic field similar to that generated by a static self-concentrating deflection yoke according to the prior art.

FIG. 2 shows a deflection system 10 having an embodiment of the present invention.
It indicates 0, and a lens action on the electron beam that attempts to converge the beam spot in the direction of deflection is generated in the main deflection area of the yoke 55. The deflection system 100 of FIG. 2 can be used, for example, in a television receiver. Deflection system 10
0 is, for example, 25V110 type CRT110 with a maximum deflection angle of 100 °
Contains. CRT 110 has a longitudinal axis Z perpendicular to display screen 22. The display screen 22 is, for example, 4: 3
For example, a 25-inch observation screen having an aspect ratio of

The neck end 33 of the CRT 110 houses an electron gun 44 that generates three electron beams. The electron beam generated by the gun 44 is modulated according to each of the video signals R, B and G to produce an image on the display screen 22. A given one of these beams produces a spot 999 which, when scanned, displays the display screen 2
Form a raster of the corresponding color on 2 above.

The deflection yoke 55 embodying aspects of the present invention includes, for example,
It is of the saddle-saddle-saddle type and is mounted on the CRT 110. Deflection yoke 55 partially shown in section
Is a pair of saddle-shaped coils surrounding a part of the neck 33 of the CRT and a part of a conical part, that is, a part that expands in a morning glory shape.
The line formed by 10, i.e., the horizontal deflection yoke structure
Contains 77. The deflection yoke 55 further includes a vertical, formed by a pair of saddle-shaped coils 99 surrounding the coil 10,
That is, it also includes the field deflection coil assembly 88. Further, the deflection yoke 55 is a quadrupole coil structure formed by a pair of saddle-shaped coils 11 surrounding the coil 99.
Contains 28. The deflection yoke 55 has a core 66 made of a ferrite magnetic material and having a conical body surrounding the coil 11. The main deflection area of the yoke 55 is formed between the beam entrance end and the beam exit end of the core 66. The horizontal axis X and the vertical axis Y of the screen 22 are
It is such that when the coil 99 is not energized, the spot is located along the X axis, and when the coil 10 is not energized, the spot is located along the axis Y.

A vertical deflection circuit 177, which can be a conventional one,
Generates a vertical sawtooth current i _v coupled to the field deflection coil assembly 88 and also generates a vertical frequency parabolic signal V _pv
Generate Current i _v and the signal V _pv are synchronized with the vertical synchronizing signal V _H which is generated in a known manner. A horizontal deflection circuit 178, which may be conventional, is provided with a line deflection coil assembly 77.
To generate a horizontal sawtooth current i _y and a horizontal frequency parabolic signal V _ph . Current i _y and signal V
_ph is synchronized with the horizontal synchronizing signal F _H generated in a known manner.

According to a feature of the present invention, the yoke 55 acts as a beam deflector and also acts as an electron beam lens. The electron beam lens action of the yoke 55, which is the same for each of the three beams, will be described for only one of the electron beams. Electron beam lensing reduces spot stretching (elongation). Electron beam lensing can be obtained by generating a deflecting magnetic field having magnetic field non-uniformity. The non-uniformity of the deflecting magnetic field is such that a given cross-section in the electron beam path at the deflection yoke 55, i.e., different parts of the beam in the profile,
The lensing is effected with a somewhat different amount of deflection so as to reduce the lengthening of the spot and to reduce the tendency of the spot to increase in ellipticity. A more detailed description of how inhomogeneities in the deflecting magnetic field reduce the ellipticity of the spot will be given later.

Stigmator, which will be explained in detail later
The astigmatism correction device 24, which is called behind the yoke 55, surrounds the neck 33. Stigmatol 24 is located between gun 44 and yoke 55. The stigmator 24 generates a magnetic field having a non-uniform magnetic field on the neck 33 outside the yoke 55 to prevent astigmatism caused by the lens action of the yoke 55 to make the spot 999 anastigmatic. I do.
Spot 999 indicates that the entire area of the electron beam spot is CRT11
When focused to form a circular spot at a single level of the focusing voltage F applied to the zero focusing electrode 333, it can be considered an anastigmatic.

The coil 11 generates a negligible magnetic field when the spot 999 is located at substantially all of the corners and diagonals of the display screen 22, for example, at the 2 o'clock point, as described below. It is driven by the current iq. Thus, when the spot 999 is at a corner of the display screen 22, the electron beam lensing of the yoke 55 is substantially unaffected by the quadrupole coil assembly.

The winding distribution of the horizontal deflection coil 10 in a given plane perpendicular to the axis Z having the coordinate Z = Z1 represents the winding distribution in the main deflection area of the yoke 55. For example, display 22
A predetermined winding distribution of each of the horizontal deflection coil 10 and the vertical coil 99 is set in order to obtain the non-uniformity of the deflection magnetic field that forms a round spot at the corner of. The winding distribution parameters are set experimentally so that a round spot is obtained at each of the corners of the display screen 22, for example, at 2 o'clock. Coil in such a plane
The ten winding distribution is selected to provide a positive first ratio of about + 10% between the positive third harmonic component and the fundamental harmonic component. Such a positive first ratio represents a pincushion horizontal deflection field. By convention, for a horizontal coil, the positive sign of the third harmonic indicates a pincushion field and the negative sign indicates a barrel field. Similarly, the plane Z =
The winding distribution of the vertical deflection coil 99 in Z1 is approximately-between the magnitude of the negative third harmonic component and the magnitude of the fundamental harmonic component.
It was chosen to obtain a negative second ratio of 60%, which also shows a pincushion-shaped magnetic field. In accordance with convention for vertical deflection coils, a negative sign indicates a pincushion field and a positive sign indicates a barrel field.

The values of the first and second ratios described above are mainly, for example,
It was chosen to get a round spot 999.
Concentration error (convergence error) as described later
And geometric errors are corrected not by the yoke 55 but by another configuration. The sign of each ratio is chosen so as to obtain the required type of field non-uniformity, namely a pincushioned horizontal deflection field and a pincushioned vertical field at the corners. When the electron beam is focused by the action of the focusing electrode voltage F of the CRT 110 and made anastigmatic by the operation of the stigmator 24 (when astigmatism and image distortion are corrected to form a circular spot), the screen 999 spots at a given corner with 22
Has a shape with the optimal ellipticity. For a typical CRT, the optimal ellipticity is obtained when the spot 999 has, for example, a circular shape. Thus, the first and second ratios set the required first electron beam lens action to obtain a circular spot at the corner of the display screen 22. The yoke 55 is connected to the length of the major axis of the spot 999 at the corner of the display screen 22 and the display screen 22.
The advantage is that the ratio of the length of the major axis of the spot 999 to the center of the spot 999 is significantly smaller than the corresponding ratio in FIG. Gun 44 and stigmator 24 form an additional electron beam lensing that makes spot 999 anastigmatic.

When the spot is on the horizontal axis X of the screen, only the barrel-type horizontal deflection magnetic field is used to generate a required magnetic field gradient in the beam path to reduce the elongation of the spot, thereby setting the first electron beam lens action. can do. Similarly,
When the spot is along the vertical axis Y, only a barrel shaped vertical magnetic field can produce the required magnetic field gradient in the beam path to reduce spot elongation.

In a barrel vertical deflection field, when the spot is on the axis Y, the magnetic flux density along the axis Y generally decreases with increasing distance from the center of the screen, and in a pincushion vertical deflection field, the magnetic field gradient Is the reverse of the whole.

The magnetic field gradient or magnetic flux density gradient at the yoke 55 required to reduce the extension of the spot on the axes X and Y is mainly a saddle-shaped coil having quadrupole symmetry.
It is set by a quadrupole coil assembly 28 formed by 11. The quadrupole deflection magnetic field component generated by the coil 11 corrects for the elliptical distortion of the spot when the spot is on each axis X or Y of the display screen 22 and the long axis of the spot at the center of the screen 22. Suppress that the major axis of the spot 999 becomes longer than the length. Coil 11
Does not significantly affect the non-uniformity of the magnetic field when the spot 999 is at each corner as described later.

FIG. 3 schematically shows the magnetic flux or magnetic field generated by the coil 11 of the quadrupole 28 having a winding-current product distribution containing mainly the second harmonic component. The magnetic flux shown represents the magnetic flux in a plane or beam path region having the coordinate Z = Z1 represented by rectangle 112. The same reference numerals and numerals in FIGS. 1, 2 and 3 indicate similar elements or functions. The arrow _Hq in FIG.
When 9 is at the 3 o'clock point on the shaft end, it indicates the direction of the magnetic flux density of the magnetic field or magnetic flux component generated only by the coil 11 of the yoke 55.

When spot 999 in FIG. 2 is at the 3 o'clock point on screen 22 in FIG. 2, the magnetic field represented by arrow _{Hq in} FIG. 3 generated by coil 11 in FIG. 2 is generally horizontal. It has a direction opposite to the direction of the pincushion-type horizontal deflection magnetic field component (not shown) generated by the deflection coil 10. The strength of the magnetic field generated by the coil 11 increases in the direction of the deflection. A net (net) deflection magnetic field obtained by the vector sum of the magnetic field components due to the total operation of the two magnetic fields,
That is, an overall deflection magnetic field is generated.

The magnitude of the current iq in FIG. 2 for energizing the coil 11 is such that when the spot 999 is at the 3 o'clock and 9 o'clock points on the corresponding screen 22, each end of the horizontal axis X of the rectangle 112 in FIG. Section is large enough to change the non-uniformity of the deflecting magnetic field in the beam path. Nonuniformity of deflection magnetic field is current iq
This changes from a pincushion type to a deflection field that can be generated in the beam path with a barrel-type horizontal deflection field alone. Therefore, the net deflection magnetic field Hφ ₍₁₎ near the center point C of the rectangle 112 is stronger than the net deflection magnetic field Hφ ₍₂₎ further away from the center C. Similarly, the coil 11 of FIG. 2 provides only a barrel-shaped vertical deflection field in the beam path at each end of the vertical axis Y of the rectangle 112 when the spot 999 is at the 6 o'clock and 12 o'clock points in FIG. Generates a net magnetic field having a deflection magnetic field inhomogeneity that can be generated in the beam path.

For convenience of explanation, the beam profile or cross section 999a, which presents a substantially elliptical shape in FIG. 3, shows that the cross section of the beam in the rectangle 112 of the yoke 55 in FIG. This shows what the spot 999 in FIG. 2 would look like at the 3 o'clock point on the screen 22 in FIG. The ellipticity shown here for section 999a has been selected for illustrative purposes only. That is, for the sake of explanation, the non-uniformity of the magnetic field due to the coils 10 and 99 has been neglected because the non-uniformity of the magnetic field generated by the coil 11 is more prevalent at that position.

The magnetic field non-uniformity or magnetic flux density gradient created by coil 11, along with the magnetic flux non-uniformity created by stigmator 24, makes spot 999 of FIG. The ratio of the major axis of the spot 999 at the edge of the screen to the major axis of the spot 999 at the center of the screen 22 is substantially smaller than when the electron beam passes through a completely uniform horizontal deflection magnetic field. As a result, there is an advantage that the above-mentioned tendency that the spot shape is distorted or elliptical with respect to the round shape at the center of the screen is reduced. For example, the non-uniformity of the magnetic flux density generated by the composite barrel-type horizontal deflection magnetic field, that is, the magnetic flux density gradient, is equal to the end 108 near the center point C of the rectangle 112 of the electron beam cross section 999a in FIG.
Is longer in the direction X of deflection than the second end 109 farther from the center point C, that is, strongly deflected.
This situation, schematically illustrated by the straight arrows 108a and 109a, is due to the application of magnetic forces in opposite directions to the ends 108 and 109, respectively, as a result of the magnetic field inhomogeneity, i.e., the magnetic flux density gradient. Are equivalent. As a result, the yoke 55 in FIG.
In addition to the scanning or deflecting action, it also operates as an electron beam lens that converges the spot 999 in the direction of its extension. In the case of FIG. 3, the direction of extension is also the direction X of deflection.

Suppose that spot 999 is already focused without magnetic force as represented by arrows 108a and 109a. Arrow 108a
The effect of the beam-concentrating magnetic force, represented by and, is that the left and right ends of the long axis of the spot 999 in the direction of the horizontal axis X are overconcentrated. Therefore, the left and right ends tend to concentrate not on the screen 22, but on a plane located between the display screen 22 and the yoke 55 in FIG. As a result, along the axis X, a flare-like portion (not shown) is formed near the left end of the spot 999 in FIG. 2, and a flare-like portion (not shown) is formed near the right end of the spot 999. . Such a pair of flared portions makes the spot 999 non-circular, e.g., an elongated ellipse, i.e., astigmatic. The flare of the spot 999 created by the deflecting magnetic field at the yoke 55 can be eliminated by using the stigmator 24 and / or the gun 44 of FIG.

The stigmator 24, which is farther from the screen 22 than the yoke 55, causes a magnetic field inhomogeneity that tends to diverge the cross section 999a in FIG. This is in contrast to the beam focusing operation of the yoke 55 in the direction of the axis X. As a result, spot 999 is maintained anastigmatically. By causing the beam convergence operation to be performed closer to the screen 22 and the beam divergence operation to be performed at a position farther from the screen 22, the length of the major axis of the spot 999 is reduced as shown by the broken circle in FIG. Decrease. A similar electron beam lensing action that causes the spot 999 to converge in the direction of deflection or extension is caused by the operation of the coil 11 when the spot 999 is at the 12 o'clock, 9 o'clock and 6 o'clock points.

For a given direction of deflection φ, the net deflection magnetic field in the electron beam path is azimuthal as shown in FIG. 3 in a direction generally perpendicular to the direction of deflection.
It has a component Hφ. In order to reduce the elongation of the major axis of the spot 999, the component Hφ in the yoke 55 near the electron beam
Decreases as the distance from the center point C in the direction of deflection increases. Thus, if one seeks to obtain such a magnetic field gradient of the magnetic field component Hφ when the spot 999 is located on one of the axes X and Y of the screen 22, such a magnetic field gradient becomes positively isotropic ( requires field non-uniformity created by a horizontal or vertical barrel-shaped deflection field that causes isotropic astigmatism. For example, the magnetic field component Hφ in FIG.
Decreases as the distance in the direction of deflection from center point C along axis X increases. On the other hand, in order to obtain such a magnetic field gradient when the spot 999 is located at the corner of a display screen having a 4: 3 aspect ratio, such a magnetic field inhomogeneity can be reduced to a pincushion horizontal deflection magnetic field. It is formed by a combination with a pincushion vertical deflection magnetic field. If the aspect ratio is different from 4: 3, another type of magnetic field shape will be required to obtain such field non-uniformity at the corners.

The required winding-current product distribution in the first quadrant of the coil 11 of FIG. 2 is shown in FIG. 4 as a function of the angle α. The angle α is measured from the axis X. Similar symbols and numerals in FIGS. 1, 2, 3 and 4 denote similar elements or functions. Each vertical bar in FIG. 4 represents a winding slot in the first quadrant of the coil 11 having a total angular width of 6 degrees. Each slot accommodates a bundle of conductor windings of each coil portion. Thus, fifteen slots cover the entire 90 ° of the first quadrant. The height and position of the bar with respect to the axis
Represents the magnitude and sign of the winding-current product NI produced by each bundle in the slot. Coil 11 in FIG.
Has substantially only the second harmonic component defined by the Fourier series.

In order to obtain one of the polarities of the harmonic component of the second harmonic of the winding-current product, the current iq in FIG.
It is caused to flow in a predetermined direction in a corresponding bundle of conductor windings of the coil 11 between the entrance area and the exit area of the yoke. On the other hand, at the same time, the current iq is simultaneously made to flow in the opposite direction to the second conductor winding bundle of the coil 11 in order to obtain the other polarity of such a harmonic component.

As a function of the position of spot 999 on screen 22,
Dynamically altering the strength of the quadrupole magnetic field generated by the coil 11 and providing the appropriate magnetic flux direction, the magnetic field of the yoke 55 at the corners of the display 22 is substantially changed by the quadrupole assembly 28. It would be desirable to have no effect. In this way, the control of the spot size at the corner is not the winding distribution selected for the coil 11, but
This is done by the winding distribution selected for coils 10 and 99, while the spot size is selected for coil 11 rather than the selected winding distribution for coils 10 and 99 when the spot is on axis X or Y. This has the advantage of being controlled by the winding distribution. The dynamic change is used to obtain the required magnetic field inhomogeneity as a function of the beam landing position of spot 999 on screen 22.

In order to generate a current iq that dynamically changes the quadrupole magnetic field generated by the coil 11, the waveform generator 101
Generate 101. Signal v101 is coupled to a current driver 104, which can operate as a linear amplifier, producing a current iq that is linearly proportional to signal v101. The signal v101 is represented by (k1 · vpv) + (k2 · vph), which is the sum of product terms expressed in the form of an equation. Claim vpv and vph represent the instantaneous values of signals V _pv and V _ph, k1 and k2, as described later, of the required waveform current
is a predetermined constant selected to obtain _iq .

The signal V _pv generated by deflection circuit 177 is zero when spot 999 is located in the center of the vertical trace and has a positive peak when spot 999 is at the top or bottom. Also, as shown by the waveforms in FIG.
The signal _Vph generated by the deflection circuit 178 is zero when the spot 999 is located in the center of the horizontal trace and has a negative peak when the spot 999 is located on the left or right side of the screen 22. . Thus, the current iq is the signal
It includes the sum of a parabolic current component according to V _ph and a parabolic current component according to signal V _pv . A waveform generator capable of generating such a waveform is described in U.S. Pat. No. 4,683,405 in the name of Truskalo et al. (Hereinafter "Trusukalo Patent"), which is hereby incorporated by reference. (PARABOLIC VO
LT GENERATING APPARATUS FOR TELEVISION).

5a to 5d show waveforms useful for explaining the operation of the device of FIG. FIG. 1, FIG. 2, FIG. 3, FIG.
Similar symbols and numbers in FIGS. 5a-5d represent similar elements or functions.

The constants k1 and k2 of the generator 101 in FIG. 2, for example, when the sum of the parabolic current components is such that the spot 999 is located near the corner of the screen 22 in FIG. The values are selected to be substantially equal so as to produce a current iq that is small or substantially zero. Therefore,
The quadrupole magnetic field generated by the coil 11 is negligible, for example, as described above, so as not to affect the shape of the spot 999 when the spot 999 is near the top of the screen 22 or near the diagonal. Will be. Therefore, spot 999 at the corner of screen 22
Is determined mainly by the harmonic component of the negative third harmonic generated by the vertical deflection coil and the positive third harmonic generated by the horizontal deflection coil. The values of the constants k1 and k2 of the generator 101, which determine the magnitude of the current iq peak in FIG. 5c, are the required values for the quadrupole field of the coil 11 when the spot 999 is at the 3 o'clock and 9 o'clock points. The size and polarity are selected to obtain.

In the configuration of FIG. 2, for a given value of the constants k1 and k2, the magnitude of the quadrupole field when the spot 999 is at the 6 o'clock or 12 o'clock point is also constant. If necessary, using another waveform generator in place of the generator 101, changing the non-uniformity of the magnetic field generated by the quadrupole coil 11 in a manner not shown, for example, the coil The strength of the magnetic field at the twelve o'clock point generated by 11 can be set independently of the strength of the magnetic field at the three o'clock point.

In a self-concentrating yoke, spots on axis Y at a given distance from the screen center are less elliptical than spots formed at the same distance on axis X, ie, they are more circular. This is because in the self-concentrated yoke, the non-uniformity of the vertical deflection magnetic field is already in a barrel shape in order to obtain concentration. But,
Unlike the configuration of FIG. 2, the self-concentrating yoke has a disadvantage that the degree of magnetic field non-uniformity is not optimized to obtain a round spot.

In the configuration of FIG. 2, the corresponding winding-current product distribution at a given beam landing position is 3
A choice is possible for each of the three coils 10, 99 and 11. The ability to select it for each of the three deflection coils provides more freedom to set the required field inhomogeneity. A higher degree of freedom provides a total improvement in reducing spot elongation, for example, as compared to when the winding-current product distribution can only be selected for one coil.

For example, when the spot 999 is on the axis X, the net effect of the magnetic field in the beam path in the yoke 55 determined primarily by the coil 11 is similar to that produced by only the barrel-type horizontal deflection magnetic field. On the other hand, the horizontal deflection coils of the self-concentrating yoke cause magnetic field inhomogeneities that cause unwanted electron beam lensing. This is because such a magnetic field non-uniformity is a pincushion type in the self-concentrating yoke, unlike the configuration shown in FIG. The pincushion vertical deflection magnetic field is substantially positive trap concentration and positive anisotropic astigmatism error, as will be described below, which is corrected using another configuration rather than at the yoke 55. Tend to occur. On the other hand, in a self-concentrating yoke in which the vertical deflection magnetic field required for the purpose of obtaining concentration is a barrel type, trap errors are reduced in the yoke. When spot 999 is on axis Y, the net effect of the magnetic field in the beam path determined primarily by coil 11 is similar to that produced by the barrel-shaped vertical deflection field.

Coils 10 and 99 in the electron beam entrance area of yoke 55
Are selected to prevent distortion of the spot, referred to as "spot coma". The spot coma is the difference in distance between the center of the beam and the midpoint between the ends of the beam when the beam is deflected. Spot coma is caused by factors similar to those of concentrated beams of three beams. For example, spot coma occurs due to, for example, non-uniformity of the magnetic field in the intermediate region. The entrance area has the greatest effect on spot coma. To prevent spot coma, the winding distribution is such that the sign of the third harmonic component of the winding distribution in the entrance region of each of the resulting coils 10 and 99 of the yoke 55 is the same as that of the intermediate deflection region of the yoke 55. Of the winding distribution related to
It is shaped so as to be opposite to the sign of the harmonic component.

As mentioned above, in the middle or main deflection region of the yoke 55, each of the magnetic fields generated by the coils 10 and 99 is generally pincushion-shaped to form a rounded spot. On the other hand, when the spot is on the horizontal or vertical screen axis X or Y, the pincushion-type deflection magnetic field is undesirable because it unacceptably stretches the spot in the direction of deflection.

According to another aspect of the present invention, the stigmator 24 of FIG. 2 cooperates with the yoke 55 to create an anastigmatic spot. Stigmatol 24 includes a double quadrupole coil configuration forming an electromagnet having eight poles. The double quadrupole coil configuration of the stigmatol 24 of FIG. 2 is shown in FIGS. 6a and 6b, respectively. FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG.
The same reference numerals and numbers in FIGS. 5d and 6a to 6b indicate similar elements or functions. 6b forming four magnetic poles 224 is energized by current ia. The quadrupole coil 24b of FIG. 6a, which forms a magnetic pole 124 alternating therewith, is energized by the current ib. The quadrupole coil 24a in FIG. 6b corrects astigmatism in the directions of the axes X and Y as a whole. The quadrupole coil 24b is rotated 45 degrees with respect to the quadrupole coil 24a. The coil 24b, as a whole,
For example, astigmatism in a direction forming an angle of +45 degrees with respect to the axis X, in this case +45 degrees with respect to the axis X or Y as a whole.
The correction is made by applying a magnetic force in a direction forming an angle of degrees. The magnitude and waveform of the current ia and ib of the stigmator 24 and the current iq flowing through the coil 11 of the yoke 55
When at the corners of 22 and along the axis, an anistigmatic beam spot is selected to be obtained. By using the double quadrupole coil configuration of the stigmator 24, the total quadrupole field generated by the stigmator 24 is dynamically changed by a predetermined angle with respect to the axis X as a function of the spot landing position. , Can be electrically rotated.

A waveform generator that can be similar to that shown in the Tulucaro patent to generate the current ia required for astigmatism correction of the spot 999 in the directions of the axes X and Y.
102 generates a signal v102 which is coupled to a current driver 105.
The current driver 105 can operate as a linear amplifier. The signal v102 can be represented by, for example, the following formula: (k3 · vpv) + (k4 · vph) + (k5 · vpv · vph) + k6. k3, k4, k5 and k6 are predetermined constants selected to obtain the required waveform. The constant k3 is set to reduce the spot astigmatism when the spot is located at the 12 o'clock point on the display screen 22 of FIG.
It has been selected to generate a current ia of the level shown in FIG. 5d. The constant k4 is selected to produce the current ia of FIG. 5d at a level that reduces spot astigmatism at the 3 o'clock point. The constant k5 is selected to produce a level of current ia that reduces the spot astigmatism at the 2 o'clock point. DC
The constant k6 representing the current is selected to produce a level of current ia that reduces the spot astigmatism in the center of the display screen 22.

The current ib is supplied to the quadrupole coil 24b and the axis X or Y
The astigmatism of the spot 999 in the direction forming an angle of 45 degrees with respect to is corrected. To generate the current ib, the waveform generator 114
Generates the signal V114. The signal V114 has the formula (k7 · vpv · vph)
+ K8. The terms k7 and k8 are
Is a predetermined constant selected to obtain a required waveform for correcting the astigmatism of the spot 999 at the corner of. The generator 114 is described in U.S. Pat. No. 4,318,032, entitled "Convergence Circuit Included A QUADRANT SEP," in the name of Kureha.
ARATOR)].

7a to 7e show illustrative waveforms for the operation of the generator 114 of FIG. FIG. 1, FIG. 2, FIG. 3, FIG.
Figures, 5a to 5d, 6a to 6b and 7a to 7e
In the figures, like symbols and numbers indicate like elements or functions. The current ib in FIG. 7a has a peak value each time the spot 999 in FIG. 2 comes near the corner of the display screen 22. The current ib in FIG. 7a has a spot 999, while FIGS. 7a and 7b
As shown in FIG. 7, FIG. 7c, it is 0 when it is at the center of the display screen 22, and, as shown in FIG.
0 when 999 is near the X and Y axes of the display screen 22
It is. The phase of the current ib changes polarity each time the spot 999 of FIG. 2 crosses the horizontal axis X at the vertical center of the screen 22.

A dynamic focusing voltage F is applied to the focusing electrode 333 of the CRT 110 to focus an anastigmatic spot generated by the yoke 55 and the stigmator 24. The waveform generator 103, which can be similar to that described in the Tulucaro patent, has the formula (k9 · vpv) +
Generate a signal v103 represented by (k10.vph) + (k11.vpv.vph). The constants k9, k10 and k11 are chosen to obtain the required focusing action. The signal v103 is the focusing voltage F
Is coupled to a focused voltage generator and modulator circuit 106 for generating The voltage F is dynamically modulated in proportion to the signal v103.

The advantage is that a circular spot for a given electron beam can be generated at the CRT 110 of FIG. 2 with a very large beam current, eg, 3 mA. Also, by dynamically changing the non-uniformity or astigmatism of each of the deflection magnetic fields in the yoke 55, the beam spot is focused, made anastigmatic, and circular as shown in FIG. Closed shape. Such an advantageous electron beam lens action is monochrome
Can also be used for CRT. The type of field non-uniformity of the horizontal or vertical deflection field that can produce a circular spot at each corresponding time point is also shown in FIG. First
5, FIG. 2, FIG. 3, FIG. 4, FIGS. 5a to 5d, FIGS. 6a to 6b, 7a to 7e, and FIG. Indicates an element or function. As shown in FIG. 8, the variation in the size of the spot generated by the arrangement of FIG. 2 as a function of the spot position is much smaller than that shown in FIG. As mentioned earlier, the spot shown in FIG. 1 is formed by a yoke that generates a uniform magnetic field. Thus, in FIG. 1, when the spot is at the end of the horizontal axis, the major axis length of the elliptical spot is 1.48 times the diameter of the substantially circular spot at the center of the display screen. On the other hand, in FIG. 8, the maximum increase is only 1.18 times. The advantage of the spot generated by the arrangement of FIG. 2 that the variation of the ellipticity as a function of the spot position is considerably smaller than that shown in FIG. 1, as shown in FIG.

FIG. 9 shows a deflection system embodying another embodiment of the present invention.
100 ', and the lens action on the electron beam is yoke 5
Generated at 5 '. FIG. 1, FIG. 2, FIG. 3, FIG.
5a to 5d, 6a to 6b, 7a to 7e, 8 and 9, the same reference numerals and numbers indicate the same elements or functions. The deflection system 100 'is a CRT 11 shown in FIG.
Includes CRT 110 ', which can be similar to 0. The deflection yoke 55 'having the features of the present invention is a CRT 11
It is attached to 0 '. A deflection yoke 55 ', which is partially shown in cross section, has a line deflection formed by a pair of saddle coils 10a surrounding a part of the neck 33' of the CRT 110 'and a pair of saddle coils 10b surrounding the saddle coil 10a. A yoke structure 77 'is included. The deflection yoke 55 'also includes a pair of saddle-shaped coils 99a surrounding the coil 10b and this coil 99a.
and a field deflection coil assembly 88 'formed by a pair of saddle coils 99b surrounding a.

The coil 10 in the electron beam entrance area of the yoke 55 '
The winding distribution for each of a, 10b, 99a, and 99b is selected to prevent distortion of the spot, formerly referred to as spot coma. A core 66 ', which forms part of a conical body and made of ferrite magnetic material, surrounds the coil 99b. A stigmator 24 ', which can be similar to the stigmator of FIG. 2, performs a similar function.

In the middle and exit regions of the yoke 55 'in FIG. 9, the winding-current product distribution of the windings forming the coil 10a, ie the angular density of the windings, is the fundamental harmonic defined by the Fourier series expansion. It changes according to the sum of the component and the harmonic component of the positive third harmonic. The ratio of the magnitude of the third harmonic component to the fundamental harmonic component of the winding-current product distribution of the coil 10a is set to about + 90%.

On the other hand, the winding distribution, that is, the angular density of the windings forming the coil 10b is made to change according to the sum of the fundamental harmonic component defined by the Fourier series and the harmonic component of the negative third harmonic. . The ratio between the magnitude of the third harmonic component of the winding-current product distribution of the coil 10b and the magnitude of the fundamental harmonic component is set to about -110%.

The horizontal deflection circuit 178 'generates a horizontal deflection current iya in the coil 10a, and a horizontal current iyb flows in the coil 10b. Current iy
“a” causes the winding-current product distribution of the coil 10a to include a harmonic component of a third harmonic having a predetermined polarity and also a fundamental component. Similarly, current iyb causes the harmonic component generated by coil 10b to include a third harmonic component and a fundamental harmonic component of opposite polarity.

The ratio of the magnitude of the currents iya and iyb is controlled and varies as a function of the position of the spot on the screen 22. This change in ratio changes the magnetic flux density gradient, or non-uniformity, of the horizontal deflection field generated by the combined structure of coils 10a and 10b as a function of spot position. Depending on the selected specific ratio of the magnitudes of the currents iya and iyb, the combined configuration of the coils 10a and 10b produces an overall pincushion horizontal deflection field or an overall barrel horizontal deflection field Is determined. This current ratio determines the magnitude and sign of the first sum, which is the sum of the third harmonics of the combined configuration of the coils 10a and 10b.

The ratio of the magnitudes of the current iya and iyb also depends on the coils 10a and 10b
Is determined as the second sum, which is the sum of the fundamental harmonic components of the combination configuration. The third ratio is defined as the ratio of the first and the second sum. Therefore, the third ratio is the third of the horizontal frequency deflection field.
It is defined as the ratio of the sum of the harmonic components of the harmonic to the sum of the fundamental harmonic components. This third ratio indicates the type and degree of magnetic field non-uniformity generated by coils 10a and 10b. For example, as the current iya increases and the current iyb decreases, the third ratio becomes more positive and the resulting horizontal deflection magnetic field has a stronger pincushion shape.

According to a feature of the invention, the ratio of the current iya to iyb is controlled to change dynamically as a function of the spot position on the screen, and the magnitude and orientation of the third ratio is changed. By changing the third ratio, the coils 10a and 10b
The degree and type of the non-uniformity or astigmatism of the overall horizontal frequency deflection magnetic field generated by the above change. By changing the third ratio, the horizontal deflection magnetic field can be made stronger or weaker as a function of spot position to provide a dynamic electron beam lens action, in a pincushion-shaped or stronger or It can have a stronger barrel shape. By modulating the currents iya and iyb, an effective lens action to control the shape of the beam spot can be obtained in a manner similar to that described with respect to the circuit of FIG.

Changing the ratio of the magnitudes of the current iya and iyb in FIG.
Although not shown in detail, the modulation is performed by the modulation circuit of the horizontal deflection circuit 178 '. The circuit 178 'amplitude modulates each of the currents iya and iyb at a vertical frequency according to the corresponding waveforms 178a and 178b, respectively. Each of the currents iya and iyb can be modulated in a manner similar to that performed by a conventional lateral pincushion distortion correction circuit. The modulation waveforms 178a and 178b may use vertical frequency waveforms. With such modulation,
The magnitude and sign of the third ratio change dynamically as a function of the spot position. This modulation provides an effective lensing to control the shape of the beam spot.

Similarly, in the middle and exit areas of the yoke 55 ', the coils
The winding distribution or angular density of the windings forming 99a is adapted to vary according to the sum of the fundamental harmonic components defined according to the Fourier series and the sum of the positive harmonic components of the third harmonic. . For example, the ratio of the magnitude of the third harmonic component to the fundamental harmonic component of the winding distribution of the coil 99a is approximately +200.
Set to%.

On the other hand, the winding distribution or angular density of the windings forming the coil 99b is defined by Fourier series expansion,
It changes according to the sum of the fundamental harmonic and the sum of the harmonic components of the negative third harmonic. For example, the ratio between the magnitude of the third harmonic component of the winding distribution of the coil 99b and the magnitude of the fundamental harmonic component is set to about -200%. The vertical deflection circuit 177 'generates a vertical deflection current iva for the coil 99a and a vertical deflection current ivb for the coil 99b. According to a feature of the invention, the ratio of the magnitude of the currents iva and ivb, which varies as a function of the position of the spot on
Determines the overall formation of the pincushion-type vertical deflection magnetic field or the barrel-type vertical deflection magnetic field, and determines the magnetic flux density gradient or magnetic field of such a vertical deflection magnetic field. Also determine the degree of non-uniformity. Current
The ratio of iva to ivb changes dynamically to provide a dynamic electron beam lensing effect. The fourth ratio is defined in a manner similar to the third ratio, as described above for coils 10a and 10b. The fourth ratio is defined as the ratio of the sum of the third harmonic component and the sum of the fundamental harmonic components for 99a and 99b. Dynamic electron beam lensing can be further achieved by changing the fourth ratio associated with coils 99a and 99b in a manner similar to that described above for coils 10a and 10b.

In accordance with yet another aspect of the invention, the ratio of currents iva and ivb is driven by a modulation circuit that modulates the amplitude of each of currents iva and ivb according to corresponding waveforms 177a and 177b, respectively, although details thereof are not shown. Can be changed. Current iva
And ivb can be modulated in a manner similar to that performed by conventional upper and lower pincushion distortion correction circuits.
Modulated waveforms 177a and 177b can include vertical and horizontal frequency waveform components.

Dynamically change the non-uniformity of each of the horizontal and vertical deflection magnetic fields at the yoke 55 ', dynamically change the non-uniformity of the magnetic field generated by the stigmator 24', and dynamically change the focusing voltage. By varying, the beam spot is focused, anastigmatic, and rounded, as shown in FIG. FIG. 1, FIG. 2,
3, 4, 5 a to 5 d, 6 a to 6 b,
In FIGS. 7a to 7e and FIGS. 8 to 10, the same reference numerals and numbers indicate the same elements or functions.

As a result of the useful lens action of the yoke 55 ', the variation in spot size and ellipticity produced by the arrangement of FIG. 9 as a function of spot position, as shown in FIG. It is much smaller than shown. As mentioned earlier, the spot shown in FIG. 1 is formed by a yoke that produces a uniform magnetic field. For example, the ratio of the major axis length of the spot at the 3 o'clock point in FIG. 1 to that at the center of the screen is 1.48, indicating a significant increase in the length dimension. In contrast, the tenth
The ratio in the figure is only 1.2. In FIG. 10, 1
The corresponding ratios at the two o'clock and two o'clock points are 1.15 and 1.2, respectively.
2

In FIG. 10, for example, at respective points of 12:00, 2:00 and 3:00, the ratio of the length of the major axis of the spot to the minor axis of the spot is 1.0, 1.07 and 0.98, respectively. Such a ratio is close to 1, indicating a round spot. On the other hand, in FIG. 1, the above ratio is 1.5 or more, indicating that the spot is considerably long, that is, a distorted spot.

FIG. 10 shows at each time point the shape of the spot obtained with the arrangement of FIG. 9 and the type of magnetic field inhomogeneity required to obtain such a round spot. Thus, when the spot is located along the axis X or Y of the display screen, as in the configuration of FIG. 2, the horizontal and vertical deflections required to obtain such a circular spot The magnetic fields are each barrel-shaped. on the other hand,
At the corners of a display screen having a 4: 3 aspect ratio, the horizontal and vertical magnetic fields required to obtain a round spot are each pincushion-shaped.

When the spots are at two, three and twelve o'clock, with the deflection in the configuration of FIG. 9, only a slightly larger major axis is needed to obtain a nearly circular beam spot. The deflection magnetic field non-uniformity in the electron beam path in the main deflection area of the yoke 55 'in FIG. 9 is the same as that required for the configuration in FIG.

FIG. 11 shows the configuration of FIG.
When there is a spot at the end of the yoke 55 ', mainly barrel-shaped, needed to obtain the best spot
In the main deflection region of the shows the magnetic field distribution function H ₂ and V _2. FIGS. 1 to 4, FIGS. 5a to 5d, FIGS. 6a to 6b, 7a
The same reference numerals and numbers in FIGS. 7 to 7 and FIGS. 8 to 11 indicate the same elements or functions. At the entrance area of the yoke 55 'in FIG. 9, both magnetic fields are of the pincushion type for performing spot / coma correction.

FIG. 12a shows that when the spot is at the 2 o'clock point in FIG.
9 shows the winding-current product distribution of a pair of coils 10a and 10b in the main deflection region of the yoke 55 'of FIG. 9 required to form a third ratio of + 10%. FIG. 12b shows the winding-current product distribution of coils 10a and 10b required to produce a third ratio of -30% when the spot is at the 3 o'clock point.
FIG. 12c shows the winding-current product distribution of a pair of coils 99a and 99b in the main deflection area of the yoke 55 'of FIG. 9 in an example assuming that a fourth ratio of + 60% is required. Is shown. As indicated earlier, the fourth ratio required when the spot is at the 12 o'clock point is only + 40%. FIG. 12d shows a similar winding-current product distribution of coils 99a and 99b necessary to obtain a fourth ratio of a value of -60% when the spot is at the 2 o'clock point. FIG. 1, FIG. 2, FIG. 3, FIG.
Figures, Figures 5a to 5d, Figures 6a to 6b, Figures 7a to 7e
In the figures, FIGS. 8-11, and FIGS. 12a-12d,
Like numbers and numerals indicate like elements or functions. The winding-current product distribution supplied in the other three quadrants is similar to that in the first quadrant.

12a to 12d, the winding-current product distribution is shown as a function of the angle α. In each of FIGS. 12a to 12d, each vertical bar represents a winding slot of a respective coil having a total width of 6 degrees and contains a bundle of conductor windings of the respective coil. Thus, 15 slots cover the entire 90 degrees of the quadrant. The height of this bar indicates the value of the winding-current product carried by each bundle in the slot of the coil. The black bar represents the winding winding-amp product associated with the pair of deflection coils containing the positive third harmonic, while the white bar represents the pair of windings containing the negative third harmonic. Fig. 4 shows a winding-amp product of a bundle associated with a deflection coil.

The geometrical distortion such as horizontal and vertical concentration and left / right or up / down pincushion distortion can be obtained by using, for example, a harmonic component or a magnetic field nonuniformity in a deflection yoke for the configuration in FIGS. 2 and 9. Can be corrected by a known method that does not require For example, in the configuration of FIG. 2, video signal processor 222 has signals R, G and B
Generate Each of the signals R, G, and B in a given screen frame can be split into pixel signals and stored separately in memory. Varying the time at which the individual pixel signals of each of the signals R, G and B are read out and applied to the respective cathode of the CRT 110 as a function of the position of the spot so as to prevent the aforementioned concentration or geometric distortion. Can be. One example of a circuit that corrects a similar error by changing the timing of the pixel signal is Casey, which is referenced here.
No. 4,730,216, entitled "RASTER DISTORTION CORRECTION CIRCUIT".

FIG. 13 shows a deflection system 100 "having yet another embodiment of the present invention. FIG. 13 and FIGS. 1 to 4, 5a to 5d, 6a to 6b, 7a to 7e, 8 to
Similar reference numerals and numbers in FIGS. 15 and 12a to 12d denote similar elements or functions. The deflection system 100 ″ of FIG. 13 differs from the deflection yoke 55 of FIG.
Deflection yoke 55 "for generating uniform horizontal and vertical deflection magnetic fields
Contains. The electron beam lensing action is generated in the configuration of FIG. 13 by a pair of quadrupole configurations 424 and 324 that operate similarly to the operation of the quadrupole doublet. Each of the quadrupole configurations 424 and 324 can be configured as a double quadrupole, in a manner similar to that of the stigmator 24 of FIG.

The configuration 324 in FIG. 13 is along the axis Z, and the configuration 324 is more configured.
To be closer to the display screen 22 ″ than 424,
Arranged coaxially with configuration 424. Configuration 324 is a deflection yoke
It may be located closer to the display screen 22 "than 55" or may be configured as shown by the dotted line.
Instead of 324, a configuration 324a similar to configuration 324 may be disposed between configuration 424 and yoke 55 ″.

In another embodiment of the invention, a double quadrupole arrangement 324 can be provided in the yoke 55 ". In this manner, each quadrupole of the double quadrupole is a coil of FIG.
It can be configured in the same way as described above for the eleven quadrupole windings. The axes of a pair of quadrupoles that constitute a double quadrupole are +45
゜.

In embodiments of the invention where each of the configurations 424 and 324 is configured as a double quadrupole, each of the paired double quadrupole configurations 424 and 324 produces a pair of quadrupole deflection magnetic fields. One of the quadrupole fields of each pair of double quadrupole configurations 424 and 324 can be represented as being formed by four magnetic poles qa, as shown in FIG. In FIG. 14 and the previous figures, the same reference numerals and numbers indicate the same elements or functions. The pole qa in FIG. 14 is the magnetic pole 124 in FIG. 6a.
Is the same as The other of the paired quadrupole fields can be represented as being formed by four magnetic poles qb of FIG. 14, similar to magnetic pole 224 of FIG. 6a. One pair of magnetic poles qa in FIG. 14 is on axis X. The other pair of magnetic poles qa is on axis Y. One pair of magnetic poles qb is on axis V which forms an angle of +45 degrees with axis X. The other pair of poles qb is on axis W perpendicular to axis V.

The quadrupole magnetic field generated by the pole qa of the double quadrupole configuration 424 of FIG. 13 is dynamically controlled by a current i ₁ similar to the current ib of FIG. 6a. Double quadrupole configuration 42 in Fig. 13
4, the quadrupole field produced by magnetic poles qb shown in FIG. 14 is dynamically controlled by the same current i ₂ and current ia of Figure 6b.

Currents i ₁ and i ₂ controlling double quadrupole configuration 424 of FIG. 13
Determines the total quadrupole field generated by the configuration 424. Such a full quadrupole magnetic field is a superposition of a pair of quadrupole magnetic fields generated by the magnetic poles qa and qb. Thirteenth
The total quadrupole field of each of the illustrated configurations 424 and 324 can be represented as being formed by four magnetic poles Q defining axes M and N of FIG. For example, the strength, polarity and direction of the full quadrupole field generated by the configuration 424 depends on the magnitude and polarity of the currents i ₁ and i ₂ . Thus, the angle β between the axis M and the axis X of the magnetic pole Q, and the polarity and intensity of the full quadrupole field change as a function of the currents i ₁ and i ₂ ,
i ₁ and i ₂ vary as a function of the landing position of the beam spot. Current i ₃ and i _4, respectively, to dynamically control double quadrupole arrangement 324 in a manner similar to the current i ₁ and i _2.

The total quadrupole field of each of the configurations 424 and 324 has four corresponding divergence axes D with 45 degrees to the axis N and corresponding convergence axes O perpendicular to this axis D shown in FIG. It can be represented by the magnetic pole Q. The axis O in FIG. 14 represents the direction in which the corresponding full quadrupole field tends to converge the electron beam cross section or profile. An example of the convergence of the electron beam profile by a quadrupole field has been described previously with reference to FIG. In FIG. 3, for example, the axis X represents such a beam convergence direction when there is a beam spot on this axis X similar to the axis O of FIG. The axis D in FIG. 14 corresponds to the configuration 42 in FIG.
4 represents the direction in which the total quadrupole field generated by the electron beam tends to diverge the electron beam profile.

FIG. 15 schematically illustrates the orientation of the convergence axis O (1) and the divergence axis D (1) of the double quadrupole configuration 424 with respect to the direction of spot elongation. As previously described with respect to FIG. 1, when a uniform deflection magnetic field is used, the direction of extension of the spot and the direction of deflection are the same. Similarly, the double quadrupole configuration 32
The directions of the convergence axis O (2) and the divergence axis D (2) of FIG. 4 are also shown. Thus, FIG. 15 illustrates the magnetic field generated by the doublet formed by configurations 424 and 324 of FIG.
In FIGS. 15 and prior figures, like numerals and numbers represent like elements or functions.

Axis D shown in FIG. 15 of the double quadrupole configuration 424 of FIG.
(1) and O (1) can be dynamically rotated as a function of the landing position of the beam spot by varying the current i ₁ and i _2. Similarly, axes D (2) and O (2) shown in FIG. 15 of double quadrupole configuration 324 of FIG.
By varying ₃ and i ₄ , the beam spot can be dynamically rotated as a function of the landing position.

According to a feature of the invention, the current i ₃ and i ₄ of FIG. 13, the first
The converging axis O (2) of FIG. 15 is controlled by dynamically rotating the entire quadrupole deflection magnetic field with respect to the axis Z of the configuration 324 of FIG.
Are dynamically maintained to be parallel to the direction of spot extension as the direction of deflection changes. In this way, the configuration 324 of FIG. 13 reduces spot elongation. The mode in which the profile of the beam spot converges in the direction of its extension to reduce the extension of the spot is as follows.
FIG. 3 is similar to that previously described.

As a result of such convergence in the direction of axis O (2), the thirteenth
The illustrated double quadrupole configuration 324 simultaneously diverges the beam spot in the direction D (2) of FIG. 15 perpendicular to the axis O (2). Due to the convergence-divergence effect of the full quadrupole deflection magnetic field generated by the configuration 324 of FIG. 13, the beam spot 999 has the advantage that it can be changed from a substantially elliptical shape to a substantially elliptical or nearly circular shape. There is. The converging lensing of configuration 324 causes spot astigmatism as a result of overconcentration in the direction of spot elongation.

According to another feature of the invention, currents i ₁ and i _{1 in} FIG.
₂ dynamically aligns the divergence axis D (1) shown in FIG. 15 of the arrangement 424 of FIG. 13 so as to be parallel to the direction of spot elongation, for example, astigmatism of the spot caused by the arrangement 324. Can be reduced. Thus, the configuration 42
4 causes the beam aperture angle in the region between the configurations 424 and 324 to be larger than the beam aperture angle in the region between the configuration 324 and the screen.

Configuration 424 of FIG. 13 far from display screen
The spot divergence effect produced by can cooperate with the spot convergence effect produced by configuration 324 closer to the display screen (both of these two effects occurring in the direction of spot extension) to reduce spot extension. it can. This point can be explained by a well-known theory derived from Helmholtz-Lagrange law that the product of the beam aperture angle and the spot size is constant. Therefore,
As described above, the beam spot divergence effect of configuration 424 increases the beam aperture angle and, consequently, reduces the spot size on screen 22 ".

In the quadrupole coil assembly 28 of FIG. 2, although not specifically shown in FIG.
軸 has a corresponding angled axis, whereby the structure
28 may add, for example, a pair of saddle-shaped coils to form a double quadrupole having eight magnetic poles. Such a structure 28 operates similarly to the configuration 324 of FIG.

Assume that the yoke 55 ″ in FIG. 13 is a self-concentrating yoke. If the arrangements 324 and 424 do not work, such a self-concentrating yoke will have a primarily horizontal spot as shown in FIG. It operates similarly to the prior art self-concentrating system of FIG. 16 and earlier figures where like numerals and numbers indicate like elements or functions, mainly to reduce horizontal spot growth. In addition, each of the configurations 324 and 424 can be configured as a single (single) quadrupole.
The convergence axis O (2) of 324 is the direction of the horizontal axis X. Similarly, the divergence axis D (1) of the single quadrupole configuration 424 is also the axis X
Direction. The poles of each such single quadrupole 324 and 424 are oriented with respect to axes X and Y in the same manner as pole 224 of FIG. 6b. The beam convergence-divergence action of the quadrupole configurations 324 and 424 of FIG. 13, each being a single quadrupole, reduces horizontal spot extension for the same reasons as previously described.

Configurations 324 and 424 have the opposite effect on beam concentration. Therefore, the extension of the spot can be reduced without greatly deteriorating the concentration of the three beams.
As a result, between the concentration of the three beams, the extension of the spot and the astigmatism, there is no significant sacrifice in the self-concentration characteristics of the deflection system compared to the spot extension obtained with a conventional self-concentrating yoke. A compromise can be set such that spot elongation is reduced. Yet another advantage is that the configuration 324
And 424 act in the opposite direction for a given electron beam, so similar waveform generators can be used in quadrupole configurations 324 and 424.
In that it can be used for biasing.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jyonson, Jeffrey Paul, New Jersey, USA 08648 Lawrenceville Tow-in-Oaks Drive 7 (72) Inventor Betis, Dennis Jan United States of America Pennsylvania 19067 Yardley Andrea Place 25 (56) References JP-A-57-199152 (JP, A) JP-A-57-152649 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 29/76

Claims (10)

(57) [Claims] 1. An evacuated glass envelope and a display screen disposed at one end of the envelope (22, FIG. 2).
And an electron gun assembly (44) disposed at another end of the envelope and generating an electron beam at each of the electron beam landing positions on the display screen to form a beam spot (999). Tube (110, Fig. 2)
A first beam landing position (2 o'clock, FIG. 1) along one of the horizontal and vertical axes (x-axis) of the display screen and a diagonal axis of the display screen; The second beam landing position (3 o'clock,
When the beam spot is deflected to FIG.
The electron beam landing position of the beam spot is changed so that the major axis (FIG. 1) of the beam spot tends to be longer than when the beam spot is deflected to the beam landing position (center, FIG. 1). Main deflection area of the beam path of the above-mentioned electron beam that changes in various forms (FIG. 2)
A first horizontal deflection coil (10, FIG. 2) and a first vertical deflection coil (99, FIG. 2) for generating a first horizontal deflection magnetic field and a first vertical deflection magnetic field, respectively. A feature is that the electron beam lens action varies according to the beam landing position so that the major axis of the beam spot is significantly reduced at each of the first and second beam landing positions. Area (Z1, 2nd
A first non-uniform magnetic field including a time-varying magnetic field portion (FIG. 3) that gives the electron beam lens action to the cross section (999a, FIG. 3) of the electron beam in FIG.
Means for generating in the first region of the beam path (11,
FIG. 2) and a second time-varying distance that varies according to the beam landing position in a second area of the beam path whose distance from the display screen is different from the first area. Electron beam lensing to generate a non-uniform magnetic field (FIG. 6b) to reduce the tendency of the beam spot to become astigmatic when the beam spot is at each of the first and second beam landing positions. Changes in accordance with the beam landing position, the beam spot stigmator (electron beam lens stigmatol) which gives the electron beam lens action to the corresponding cross section (999a, FIG. 6a, FIG. 6b) of the electron beam in the second region. 24, FIG. 2). 2. As a result of the geometry of the display screen, the major axis (FIG. 1) of the beam spot (999, FIG. 2) is aligned with the third beam landing position (center). , FIG. 1),
The beam spot has a tendency to extend when deflected to a fourth beam landing position (12:00, FIG. 1) along the other of the horizontal and vertical axes (Y axis) of the display screen. Further, the means for generating the first non-uniform magnetic field (11, FIG. 2) may include means for reducing the tendency of the major axis of the beam spot to be elongated at the fourth beam landing position. The apparatus according to claim 1, wherein the non-uniform magnetic field is changed according to a beam landing position. 3. When the beam spot is at each of the first, second and fourth beam landing positions (3, 2, 12:00, FIG. 1), the beam landing position at that time (x-axis). , Diagonal, y-axis, FIG. 1) and a direction (x-axis, FIG. 3) maintained parallel to the direction of the straight line between the center of the display screen (FIG. 1). 3. The device according to claim 2, wherein the cross section (999a, Fig. 3) is converged in the first area. 4. The first beam landing position (3)
Time, FIG. 1) is located at one end of the horizontal axis of the display screen (22, FIG. 2), and the fourth beam landing position (12:00, FIG. 1) is at the vertical axis of the display screen. 3. The apparatus of claim 2, wherein the second beam landing position (2 o'clock, FIG. 1) is located at a corner of the display screen. 4. 5. The horizontal deflection coil (10, FIG. 2) and the vertical deflection coil (99) are included in a deflection yoke including a magnetic core (66). A first non-uniform magnetic field magnetically coupled to a core, the first non-uniform magnetic field being generated in a third deflection coil (11) of the deflection yoke also magnetically coupled to the magnetic core; 3. The device according to claim 2, wherein 6. Apparatus according to claim 5, wherein said third deflection coil comprises a second horizontal deflection coil (10a, FIG. 9) and a second vertical deflection coil (99a). 7. The first and second horizontal deflection coils (10b, 1b).
0a, FIG. 9), the winding-current product distributions have the same harmonic order (third harmonic, FIG. 12a, FIG.
6. It includes a harmonic Fourier component of FIG.
An apparatus according to claim 1. 8. Apparatus according to claim 5, wherein the third deflection coil (11, FIG. 2) forms a quadrupole configuration for generating a quadrupole deflection magnetic field (11, FIG. 3). 9. When the beam spot is deflected (2 o'clock, FIG. 8) to a corner of the display screen, the first non-uniform magnetic field is a pin combined with a pincushion vertical deflection field only. 2. The device according to claim 1, wherein the device is of a type that can be generated by the cushion-shaped horizontal deflection magnetic field in the main deflection area (Z1, Fig. 2) in the vicinity of the path of the electron beam. 10. An evacuated glass envelope and a display screen disposed at one end of the envelope (22, FIG. 2).
And an electron gun assembly (44) disposed at another end of the envelope and generating an electron beam forming a beam spot (999) at each of the electron beam landing positions on the display screen. A tube, wherein the beam spot has a tendency to be distorted when the beam spot is at a first beam landing position compared to when the beam spot is at a second beam landing position; A first horizontal deflection magnetic field and a first vertical deflection magnetic field that are respectively generated in a main deflection area of the beam path of the electron beam that changes in such a manner as to change an electron beam landing position of the spot.
Horizontal deflection coil (10) and first vertical deflection coil (99)
A plurality of deflection coils comprising: a plurality of deflection coils, wherein the plurality of deflection coils generate a first non-uniform magnetic field including a time-varying magnetic field portion in a first region of the beam path; The first non-uniform magnetic field is directed to a cross-section of the electron beam in the first region in such a manner that the action of the electron beam lens varies according to the beam landing position so as to significantly reduce the tendency of the beam spot to distort. An electron beam lens function is provided, and a distance from the display screen to a second area of the beam path different from the first area is changed in accordance with a beam landing position. A second non-uniform magnetic field (FIG. 6b) that varies to reduce beam spot distortion when the beam spot is at the first beam landing position. A beam which gives the electron beam lens action to the corresponding cross section (999a, FIG. 6a, FIG. 6b) of the electron beam in the second area in such a manner that the action of the electron beam lens changes according to the beam landing position. Spot Stigmatol (2
4) and a deflection device comprising: